Epigenetic Regulators in Tumor Progression

描述（由申请人提供）：癌症进展涉及基因调控紊乱。在上皮组织如皮肤中，约90%的人类恶性肿瘤发生在皮肤中，该过程的最早步骤涉及分化和增殖基因的表达被破坏，导致预示癌侵袭的异常组织极性。在肿瘤进展过程中观察到的基因失调的全基因组性质涉及全局活性的表观遗传基因调节剂，然而，每个调节剂类别包含多种亚型，其在癌症中的具体作用尚未完全了解。在DNA甲基化的情况下，存在多个非冗余DNA甲基转移酶（DNMT），其主要通过沉默特定基因的表达起作用。DNMT作用被过去2年发现的一组基因拮抗，以积极促进DNA去甲基化。然而，DNMT及其拮抗剂在人类组织中的早期肿瘤进展中的作用尚不清楚。这个修订的建议集中在表征DNA甲基化的调节剂在早期肿瘤进展中的作用，特别是正常人表皮向侵袭性肿瘤的转化。 首先，我们将确定DNMT亚型在早期肿瘤进展中的作用。我们最近观察到DNMT 1在皮肤和其他组织的鳞状细胞癌（SCC）中错误表达，控制正常的表皮生长和分化基因程序，并调节在早期人类表皮肿瘤发生中改变的基因的重要子集。使用Ras驱动的表皮瘤形成的诱导型人类组织模型，在Aim I中，我们将测试加性DNMT模型，其中DNMT 1维持未分化增殖状态，而DNMT 3A/B/L从头沉默肿瘤抑制基因的诱导。 其次，我们将研究最近表征的DNMT拮抗蛋白的作用。最近发现，活性DNA去甲基化通过与碱基切除修复（BER）途径（MBD 4、TDG和AID/Apobec 2）和核苷酸切除修复（NER）途径（XPA、XPG、ERCC 2、TAF 12）相互作用的蛋白质进行。Gadd 45蛋白与BER和NER机制相互作用，使DNA去甲基化。为了支持DNA去甲基化介质在肿瘤发生中的潜在作用，我们最近观察到Gadd 45促进表皮分化并抑制异位肿瘤形成，这与特定基因的DNA甲基化减少有关。在目的II中，我们将检验DNA去甲基化的特异性介质抑制早期肿瘤进展的假设。 在拟议的资金结束时，我们计划描述DNA甲基化调节剂对人类组织中肿瘤进展的作用，作为未来癌症预防和治疗策略的基础。1

DESCRIPTION (provided by applicant): Cancer progression involves disordered gene regulation. In epithelial tissues such as skin, where ~90% of human malignancies arise, the earliest steps in this process involve disrupted expression of differentiation and proliferation genes, leading to the abnormal tissue polarity that presages cancerous invasion. The genome-wide nature of the gene dysregulation seen in the tumor progression process implicates globally active epigenetic gene regulators, however, each regulator class contains multiple isoforms whose specific roles in cancer are not fully understood. In the case of DNA methylation, there are multiple non-redundant DNA methyltransferases (DNMTs), which act primarily by silencing expression of specific genes. DNMT action is antagonized by a group of genes found over the past 2 years to actively promote DNA demethylation. The role of DNMTs and their antagonists in early tumor progression in human tissue, however, is unknown. This revised proposal focuses on characterizing the role of regulators of DNA methylation in early tumor progression, specifically the conversion of normal human epidermis to invasive neoplasia. First, we will define the role of DNMT isoforms in early tumor progression. We recently observed that DNMT1, which is mis-expressed in squamous cell carcinoma (SCC) of skin and other tissues, controls the normal epidermal growth and differentiation gene program and regulates a significant subset of the genes that are altered in early human epidermal tumorigenesis. Using an inducible human tissue model of Ras-driven epidermal neoplasia, in Aim I we will test an additive DNMT model in which DNMT1 maintains the undifferentiated proliferative state while DNMT3A/B/L silence de novo induction of tumor inhibitory genes. Second, we will study the role of recently characterized DNMT-antagonizing proteins. Active DNA demethylation has recently been found to proceed via proteins interacting with the base excision repair (BER) pathway (MBD4, TDG, and AID/Apobec2) and the nucleotide excision repair (NER) pathway (XPA, XPG, ERCC2, TAF12). Gadd45 proteins interact with both BER and NER mechanisms to enable DNA demethylation. In support of a potential role for mediators of DNA demethylation in tumorigenesis, we recently observed that Gadd45 promotes epidermal differentiation and inhibits ectopic tumor formation in association with diminishing DNA methylation at specific genes. In Aim II, we will test the hypothesis that specific mediators of DNA demethylation inhibit early tumor progression. At the end of proposed funding, we plan to have characterized the role of regulators of DNA methylation on tumor progression in human tissue as a foundation for future strategies for cancer prevention and treatment. 1